1. Field
The following description relates to a polarizing plate for organic light emitting diodes (OLEDs) and an optical display including the same.
2. Description of the Related Art
In an organic light emitting diode (OLED) display, light emitted from a self-luminous material and external natural light (external light) reflected by an internal reflector of the OLED display interfere with each other and may deteriorate the performance of the OLED display. To suppress such interference, the OLED display usually includes a polarizing plate.
Generally, in a polarizing plate for OLEDs, a polarizer and a retardation compensation film are inclined and aligned with each other such that an absorption axis of the polarizer and an optical axis (absorption axis) of the retardation compensation film form a certain angle with each other. This alignment enables the polarizing plate of the OLED to rotate a waveform of external light reflected by the internal reflector of the OLED display, thereby serving as an anti-reflective filter. However, the alignment between the absorption axis of the polarizer and the optical axis of the retardation compensation film is asymmetric and can cause lateral color shift during operation of the OLED.
In an attempt to mitigate such lateral color shift, a structure has been proposed, in which the polarizing plate includes two retardation films, a biaxially stretched retardation compensation film, and a λ/4 reverse dispersion film of a polycarbonate material, or a liquid crystal-type retardation compensation film. However, this structure still does not sufficiently suppress lateral color shift. As the angle of incidence of external light coming from the front of the OLED display increases, then depending on the viewing angle, color may change into blue or violet, or reflectance of the polarizing plate may increase. These changes are at least in part due to the phase retardation of RGB (Red Green Blue) which occurs due to the difference between the light path of lateral external light and the light path of external light coming from the front of the OLED display.